Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Light-detection and ranging (LIDAR) is an optical remote sensing technology that may be utilized to acquire information on a surrounding environment. The acquired information may include the distances between objects or properties of objects in the surrounding environment. A LIDAR device may be configured to illuminate the objects with light, detect light reflected from the objects, and determine information about the objects based on the reflected light. The LIDAR device may use ultraviolet, visible, or infrared light to illuminate and acquire information on a variety of different types of objects, such as metallic and non-metallic items, geological formations, and even atmospheric elements.
When a LIDAR device attempts to sense the presence of an object that is far away, a light beam, which is often a laser beam, may travel a relatively long distance (both from the LIDAR device to the object and from the object back to the LIDAR device). Because of the relatively long distance of travel, the beam is often significantly attenuated by the time it returns to the LIDAR device. In other words, a relatively small number of photons reflected by far-away objects return to the LIDAR device. This makes it relatively difficult to sense the presence of such far-away objects.
The relatively small number of photons can be detected by operating a photodetector at a high gain. For example, the photodector can be a photodiode operated at a high enough bias voltage such that a P-N junction of the photodiode becomes large enough to achieve an “avalance” effect, in which a single photon received by the photodiode can result in the excitation of many electrons. A photodiode operated under these conditions is sometimes referred to as an “avalance photodiode” or a “single photon avalanche detector.”
To achieve the avalanche effect, the photodiode may be operated at a bias voltage that is just below the breakdown voltage of the photodiode. For example, a photodiode's breakdown voltage can be determined and the photodiode can then be operated with a bias voltage that is somewhat less than the determined breakdown voltage.